Explosive volcanism on the ultraslow-spreading Gakkel ridge, Arctic Ocean

Sohn, Robert A. ; Willis, Claire; Humphris, Susan ; Shank, Timothy M.; Singh, Hanumant; Edmonds, Henrietta N.; Kunz, Clayton; Hedman, Ulf; Helmke, Elisabeth; Jakuba, Michael ; Liljebladh, Bengt ; Linder, Julia ; Murphy, Christopher; Nakamura, Ko-ichi; Sato, Taichi ; Schlindwein, Vera ; Stranne, Christian ; Tausenfreund, Maria; Upchurch, Lucia ; Winsor, Peter ; Jakobsson, Martin und Soule, Adam (Juni 2008): Explosive volcanism on the ultraslow-spreading Gakkel ridge, Arctic Ocean. In: Nature, Bd. 453: S. 1236-1238

Abstract

Roughly 60% of the Earth’s outer surface is composed of oceanic crust formed by volcanic processes at mid-ocean ridges. Although only a small fraction of this vast volcanic terrain has been visually surveyed or sampled, the available evidence suggests that explosive eruptions are rare on mid-ocean ridges, particularly at depths below the critical point for seawater (3,000 m)1. A pyroclastic deposit has never been observed on the sea floor below 3,000 m, presumably because the volatile content of mid-ocean-ridge basalts is generally too low to produce the gas fractions required for fragmenting a magma at such high hydrostatic pressure. We employed new deep submergence technologies during an International Polar Year expedition to the Gakkel ridge in the Arctic Basin at 85° E, to acquire photographic and video images of ‘zero-age’ volcanic terrain on this remote, ice-covered ridge. Here we present images revealing that the axial valley at 4,000 m water depth is blanketed with unconsolidated pyroclastic deposits, including bubble wall fragments (limu o Pele)2, covering a large (>10 km2) area. At least 13.5 wt% CO2 is necessary to fragment magma at these depths3, which is about tenfold the highest values previously measured in a mid-ocean-ridge basalt4. These observations raise important questions about the accumulation and discharge of magmatic volatiles at ultraslow spreading rates on the Gakkel ridge5 and demonstrate that large-scale pyroclastic activity is possible along even the deepest portions of the global mid-ocean ridge volcanic system.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Geowissenschaften > Department für Geo- und Umweltwissenschaften
• Themengebiete: 500 Naturwissenschaften und Mathematik > 550 Geowissenschaften, Geologie
• ISSN: 1476-4687
• Sprache: Englisch